As I remember, and I think this is Digital PDP-11 RSX11, you could have disk resident overlays, memory resident overlays, or a mixture of the two.
Memory resident overlays were a bizarre manifestation of the 16 bit program address spaces (64K each) coupled with the ability to have at least 22 bits worth of memory ( 4096K). The base, and all memory resident overlays, were loaded into memory, but the program's address space was limited to the base, one tree of memory resident overlays, and/or one tree of disk overlays. I can remember spending days on shoe-horning what we thought were huge programs to run in these tiny spaces. I have a vague recollection that disk overlays were defined using "*" and memory overlays "!". Now don't get started on core dumps :-) ---- Original message ---- >Date: Tue, 24 Jan 2012 07:42:19 -0500 >From: [email protected] (on behalf of Jerry Feldman ><[email protected]>) >Subject: Re: [Discuss] FORTRAN -> ??? >To: [email protected] > >On 01/23/2012 04:55 PM, Jay Kramer wrote: >> Excuse me if this is a stupid question given the email chain. Is it >> still possible to compile Fortran IV? Will it run on linux? I wrote a >> program in FORTRAN IV that uses overlays but other than that is straight >> forward code. >Strange. I have not heard of overlays being used in decades :-) >BTW: Before we had virtual memory, overlays were used to create a >smaller memory footprint in a fixed-memory system. > >-- >Jerry Feldman <[email protected]> >Boston Linux and Unix >PGP key id:3BC1EB90 >PGP Key fingerprint: 49E2 C52A FC5A A31F 8D66 C0AF 7CEA 30FC 3BC1 EB90 > > >________________ >_______________________________________________ >Discuss mailing list >[email protected] >http://lists.blu.org/mailman/listinfo/discuss _______________________________________________ Discuss mailing list [email protected] http://lists.blu.org/mailman/listinfo/discuss
